1. Field of the Invention
The invention belongs to the field of optical fiber communication, and more particularly to a high performance tunable laser with high speed tuning, stable wavelength, and power output.
2. Description of the Related Art
Currently, fiber optical telecommunication is employed in most modern telecommunication systems. Fiber optical network has offered unprecedented large capacity and installation flexibility and is able to support a variety of broadband applications that are under unprecedented development. Broadband tunable laser can help utilize the present fiber optical network resources more efficiently. Data traffic flow can be transferred from a congested channel to an unused channel by means of dynamic provision of a broadband network, thus Internet requirements are met. Tunable laser, which is also an important precondition for implementing a dynamic fiber optical network, is capable of establishing or changing an optical path rapidly. Tunable laser, especially the tunable laser with small size, large tuning range and high power output, has also been widely used in the fields of biology, medical apparatus and fiber sensor network, etc.
In view of these applications, an ideal tunable laser should include the following characteristics: wide tunable range, i.e. covering waveband C and (or) waveband L (approximately 1530 nanometers to 1610 nanometers); small size; fast channel switching speed (faster than 1 millisecond) between frequency interval grids of any two International Telecommunication Unions (ITU); excellent long-term performance stability (service time over 25 years); high reliability under extreme working conditions; and low power consumption and low cost for volume production.
Conventional tunable lasers falls into three types: (1) system that uses mechanical movable components, e.g. diffraction grating, prism, etalon or MEMS (Micro Electronic Mechanical System), as wavelength adjusting unit, the problem with this technology is as follows: the technology of adjusting wavelength by mechanically adjusting grating or prism angle is extraordinarily poor in resistance to mechanical shock and vibration, which can cause unstable short-term and long-term performances, and as a result, the tunable filter with movable components is unsuitable to fiber optical communication. (2) system for tuning wavelength by temperature adjustment through component heating or cooling. The problem with this technology is the low tuning speed due to its inherent characteristics of temperature tuning, so the application of such a laser is limited. (3) system that uses non-moving optical devices in the cavity for wavelength adjustment, including the use of magneto-optic device, acousto-optic device or electro-optic device, or current injection for selecting wavelength. The advantages of using acousto-optic technology includes high speed wavelength tuning by means of electric control without moving component, wide tuning range and simple structure, etc., therefore, such a system provides a viable solution for tunable lasers that meets the strict application requirements for fiber optical communication system.